Breakfast: 8:30 am- 9:00 am

General Session I: 9:00 am- 10:00 am

This study documents the effects of rising carbon dioxide accumulating in our largest carbon sink, the ocean, corroborating other studies that show widespread negative consequences for diverse marine organisms comprising mollusks, bivalves, corals, and others. These include sub-lethal effects such as reduced growth, delayed development, changed behaviors, and thinner calcium carbonate based shells. In more sensitive organisms, especially early life stages, increased mortality is also observed in laboratory conditions. These findings contain serious implications for many professions that heavily rely on commercial and artisan fishing for subsistence, especially in underdeveloped and island nations. Here in the Chesapeake Bay region, many fisherman rely on the Atlantic blue crab as a primary source of income. Laboratory results have shown both sub-lethal and lethal effects are observed in larval blue crabs after exposure to acidic conditions. In this study, larval blue crabs in the Z1 stage are placed in tanks at pH 8.1, 7.4, and 6.8 for 7 days. At the end of 7 days they are removed and changes in shell morphology are determined using morphometric analysis and a developmental index. These preliminary results show that larval blue crabs are susceptible to increased acidity, with significant developmental delays. Continued evaluation will extend and validate these results, including studies determining the effect of acidity on embryos and how cellular processes are affected.Author affiliations: Department of Environmental Sciences, University of Virginia

Marsh persistence is governed by two main responses to sea-level rise (SLR): vertical growth, and horizontal movement of salt marsh into uplands (transgression). In three salt marshes at the Virginia Coast Reserve (VCR), changes in marsh surface elevation were measured in summer 2016 using Global Positioning System (GPS) survey equipment and compared to previously established GPS elevations from 2000. In one of the three marshes, the GPS-based measurements of elevation change were compared to another method for determining elevation change (surface elevation tables). Marsh transgression was measured in two of the three marshes through a GIS analysis of satellite imagery of the marsh-upland boundary between 2002 and 2013. Transgression was the dominant process occurring along the upland boundary in Cushman’s and Indiantown marshes. At Cushman’s Landing, transgression occurred along 100% of the upland boundary, while at Indiantown transgression occurred along 95% of the boundary in 11 years. At both Cushman’s Landing and Indiantown, marsh elevation decreased over 16 years. At Cushman’s the average rates of elevation change were: -9.22 mm yr-1 (low marsh) and -7.17 (high marsh). At Indiantown the average rate of change in the low marsh was -18.73 mm yr-1 and lacks a high marsh zone. While the correlation between elevation change and transgression was not significant, the slope of the marshes may prove to be a better indicator of marsh vulnerability to sea level rise than rates of elevation change, given that transgression was greatest at Cushman’s marsh where the slope was 22 times lower than at Indiantown marsh. The marsh elevation at Phillip’s Creek (the third survey location) increased over time, but GPS-based measurements were two to five times more rapid and statistically different from rates measured by surface elevation tables. This preliminary research suggests directions for future investigation of the relationships between vertical and horizontal change in marshes with SLR.Author affiliations: Department of Environmental Sciences, University of Virginia

Food security is a global issue pressed by climate change and soil degradation. Where there is existing biomass waste, it can be pyrolyzed into biochar, a soil amendment that has proven to have the potential to increase soil nutrients and crop yield. Biochar eliminates waste that might otherwise decompose and release greenhouse gasses. If biochar is used efficiently, it could have positive effects on communities lacking access to fresh affordable food while reusing waste and decreasing the need for the addition of synthetic fertilizers.

My research studies the effects of dairy cattle manure biochar on butternut squash plants grown at the Morven Kitchen Garden just south of Charlottesville, Virginia compared to butternut squash grown without biochar. I will examine the size and mass of leaves and fruit as well as the mass and abundance of seeds. And I will analyze the leaves, fruit, seeds and soil for nutrient content (carbon and nitrogen). I will compare the results of samples taken from beds with biochar to samples from beds without biochar using an analysis of variance (ANOVA). I hypothesize that 1. The plants from beds that received biochar will have a greater number of fruit and bigger fruit, 2. Beds with biochar amended soils will have greater soil carbon and nitrogen concentrations, and 3. Plants grown in biochar amended soils will have a higher concentration of nitrogen in plant tissue.Author affiliations: Department of Environmental Sciences, University of Virginia

Gracilaria vermiculophylla is an exotic red macroalga that has invaded numerous American coastal waterways, yet little is known about its impact on local ecosystem function and hydrodynamics. In this presentation, we describe preliminary findings from combined aquatic eddy covariance and profiling acoustic Doppler velocimetry (ADV) measurements made over G. vermiculophylla mats on the Virginia (USA) coast. Two intertidal algal mats were sampled: one on a low velocity (~ 1 cm s-1) backwater tidal flat and one a high velocity (~ 25 cm s-1) flat. At each site an adjacent mudflat with minimal algal coverage was concurrently sampled for comparative analysis. Oxygen flux is often used as a proxy for carbon metabolism, so these measurements describe the carbon cycling of these systems. Profiling ADVs allow for the determination of water column velocity and turbulent stress profiles, which have important implications for sediment resuspension and mass transport. To date there have been no previous in situ studies of oxygen flux or velocity profiles of G. vermiculophylla mats, so these measurements represent the first of their kind. This study will allow us to describe how this exotic invader affects these key attributes of native ecosystems.Author affiliations: Department of Environmental Sciences, University of Virginia

Ozone pollution can alter floral scents which herbivores use to locate their host plants, potentially decreasing the herbivore’s foraging efficiency and success. Some herbivores are more likely to be vulnerable to changes in their hosts’ smell than others, and specialist insects may constitute one such group. Specialist herbivores, those that rely on just few related host plants, may have a smaller innate repertoire of scents compared to generalists foragers that cue in on a wide array of scents. Furthermore, while many generalist insects have demonstrated the ability to learn new olfactory cues, studies on specialist insects have not demonstrated the same breadth of learning.

To understand how specialist and. generalist foragers may respond to ozone-altered plumes, we tested two herbivorous beetles, the specialist striped cucumber beetle (Acalymma vittatum ) and the generalist spotted cucumber beetle (Diabrotica undecimpunctata) to ozone-altered plumes of their host plant, both before and after training them on the ozone-exposed plume of the host plant. Through a series of y-tube experiments, we determined that the specialist herbivore did not innately discern an ozone-altered plume from clean air (χ2 =.818, p=.3657), while the generalist could (χ2 =6.095, p=.0136). However, the specialist was able to associate the altered plume with a reward: after feeding on the host plant in an ozone-enriched environment, the specialist improved its discernment for the altered plume, and preferring the ozone-altered plume to pure air (𝜒2 =7.715, p=.0055). This indicates that associative learning could potentially help even a specialist herbivore like A. vittatum locate its host plants in polluted environments.Author affiliations: Department of Environmental Sciences, University of Virginia

Winds within a valley typically exhibit a diurnal pattern, blowing up valleys and slopes during the day and down valleys and slopes at night. This pattern is mainly controlled by differences in incoming radiation between the valley and adjacent plains. Transition periods occur around sunrise and sunset as these thermally-driven winds reverse direction in the valley. On 21 August 2017, a total solar eclipse took place over the continental United States. In the foothills of the Blue Ridge mountains near Charlottesville, VA, the eclipse took place in the early afternoon hours, when daytime upvalley winds are typically well-established. The sudden decline in daytime heating provided quasi-laboratory conditions in which to observe the response of valley boundary layer and thermally-driven winds. We designed an observational field campaign to answer the following questions: 1) Is eclipse-induced cooling sufficient to alter valley wind patterns? 2) To what vertical extent do alterations occur? In this talk, I will present results from the field campaign, with a focus on winds that developed before, during, and after the eclipse on 21 August.Author affiliations: Department of Environmental Sciences, University of Virginia

Algal blooms alter aquatic ecosystems in numerous ways, including changes to physical, chemical, and biological components that directly impact ecosystem processes and services. Recent work has shown that algal blooms are occurring more frequently and media coverage has brought attention to bloom impacts on drinking water quality. Cyanobacterial blooms are common in eutrophied lakes and reservoirs, and certain species create toxins that can cause illness and even death in humans if ingested. In addition to producing toxins, algal blooms have strong impacts on the concentrations of the metabolic gases (oxygen and carbon dioxide), which in turn impact other ecosystem components and services (e.g. biota, carbon sequestration). In order to quantify the interactions between algal blooms and metabolism, we have deployed automated sensors in Beaver Creek Reservoir over the past eight months. Beaver Creek Reservoir (BCR) is the drinking water supply for Crozet, VA and periodically experiences algal blooms, some of which can be severe and require chemical treatment. We have observed large variations in oxygen concentrations over this study, from less than 40% of fully saturated to over 140%. Periods of high oxygen concentrations also had high rates of metabolism (primary production and respiration) and generally occurred during periods of higher algal abundance. A sharp decline in oxygen concentration occurred coincident with turnover (the physical mixing of the water column due to falling temperature) followed by a more gradual recovery of the winter. Our findings suggest that biological (algae) and physical (temperature and mixing) factors can both play significant roles in controlling metabolism in BCR. Future work will test for time lags between changes in metabolism and algal abundance that might be useful to managers, as well as the prevalence of the observed low fall/winter oxygen concentrations.Author affiliations: Department of Environmental Sciences, University of Virginia

Lunch: 11:45 am- 12:30 pm

Poster Session: 12:30 pm- 2:00 pm

Numerous lines of observational evidence suggest that Earth’s tropical belt has expanded over the late 20th century and early 21st century, pushing the subtropical dry zones poleward. It is natural to expect that this poleward displacement should be associated with drying on the poleward margins of the dry zones, but it is less clear to what degree the drying should be zonally symmetric. In this project, we adopt the usual convention of quantifying the tropical width itself in terms of zonally averaged variables. We primarily use the latitude at which the mean meridional overturning circulation at 500 hPa transitions from the thermally direct Hadley cell to the thermally indirect Ferrel cell (the latitude at which Ψ_500=0). Using the resulting time series of Hadley cell widths, we test the degree to which poleward motion of the Hadley cell boundary is associated with changes in local precipitation or sea level pressure, and the degree to which these changes are or are not zonally symmetric. We test both CMIP5 models and reanalysis products, and find that in both cases, the local changes associated with Hadley cell expansion are mostly confined to certain centers of action which lie primarily over the ocean basins. We also find that these conclusions remain valid after ENSO and other effects mediated by sea-surface temperature changes are removed. These results show that tropical expansion—measured in terms of zonally-averaged metrics—is not necessarily associated with widespread extratropical drying over land.Author affiliations: Department of Environmental Sciences, University of Virginia

While much is known about the carbon cycle during succession that follows agricultural disturbance, less understood are the dynamics of the nitrogen cycle throughout secondary succession, and how plant-available nitrogen may or may not limit vegetation transitions and net primary productivity over time. Two chronosequences at the Blandy Experimental Farm in Boyce, north-central Virginia were examined to elucidate the complexities of the nitrogen cycle over a temporal successional gradient. Each chronosequence consists of one early, one mid, and one late secondary successional field (~15 years, ~30 years, and ~100 years post agricultural abandonment, respectively). Five 10×10 m plots were established in each of the 6 fields for a total of 30 plots. Total soil nitrogen (and carbon) data were collected from soils to 20 cm depth at 10-cm intervals, and net nitrogen mineralization and nitrification were estimated using an in-situ soil core with an anion-cation exchange resin bag technique. Total C and N trend upward from early to late successional plots, while C:N ratio is highest in mid-successional plots (p<0.01). Net mineralization is highest in mid-successional plots, and net nitrification trends upwards from early to late plots. Our current study marks the first comprehensive examination of soil nitrogen dynamics including mineralization and nitrification over a successional gradient at Blandy Farm. A thorough understanding of nitrogen dynamics during secondary succession is especially important in the southeastern United States, where a large portion of previously cultivated land has been abandoned over the past century, due to advances in farming efficiency and the move westward to more fertile soils. Much of the southeastern U.S. is now undergoing secondary succession, and quality data on the dynamics of nitrogen cycling during this procession can help guide future land management decisions and carbon cycling predictions.
Author affiliations: Department of Environmental Sciences, University of Virginia

The Eastern Oyster, Crassostera virginica, is an ecosystem engineer within the intertidal zone of the Eastern Shore of Virginia. The population has been largely restored locally over the last century after dramatic population declines due to overharvesting, disease, and poor water quality. Restoration efforts have proven to be successful in some regions, while similar restoration efforts have seemingly failed in others. Although many factors have played a role in successful oyster recruitment, proper siting of restoration reefs and their elevation relative to mean sea level, and how to optimize restoration designs appear to be paramount. Therefore, my first objective is to create a technique to map oyster reefs in the Virginia Coast Reserve (VCR), using laser-based light detecting and ranging (LiDAR) elevation data, determine the accuracy of using this type of data for intertidal classification, and use the map to find correlations between reef locations and the physical environment. My second objective then focuses on a new long-term oyster restoration project at Short Prong Marsh in the VCR to understand how to optimally design restored reefs to provide the dual benefits of shoreline protections and population recruitment. Four different reef designs varying in width and height, utilizing oyster castles, were constructed to run parallel to the marsh edge. Data on wave attenuation, infauna community structure, and sediment data is taken before and after reef construction to determine how artificial reefs affect the intertidal community at this location, while potential benefits for population stabilization are determined through larval settlement. Data collected will be used to analyze which configuration provides the greatest benefits. Combined, information from both objectives provide insight on oyster restoration will be examined on fine and broad scales.Author affiliations: Department of Environmental Sciences, University of Virginia

Seagrass meadows are valued for the ecosystem services they provide, including “blue” carbon sequestration from high rates of net primary production and carbon burial in sediment. Ecosystem metabolism is an indicator of carbon balance in seagrass meadows, and therefore provides information about the impact of seagrass loss and recovery on carbon sequestration. Benthic oxygen fluxes in a seagrass meadow at the Virginia Coastal Reserve have been measured seasonally by eddy covariance over the past 10 years. These in situ measurements cover a period of ecosystem development 6-13 years after restoration of the meadow by seeding (2007-2014), a high-temperature-related die-off event in 2015, and subsequent recovery of the meadow in 2016 and 2017. This uniquely extensive dataset covering 107 full 24 hour diurnal cycles provides an unprecedented opportunity to study long and short-term drivers of seagrass metabolism as well as the resilience of seagrass habitats. The VCR LTER site is a model for temperate systems globally, and is an ideal natural laboratory to study the potential impact of warming oceans on seagrass resilience.Author affiliations: Department of Environmental Sciences, University of Virginia

Nitrous oxide (N2O) is a long-lived and highly potent greenhouse gas that also destroys stratospheric ozone. Largely attributed to changes in agricultural sources, N2O concentrations are increasing at a steady rate of 0.8 ppb y–1 globally. Emission rates of N2O remain poorly constrained, with N2O sources arguably among the most uncertain of the long-lived greenhouse gases. This study quantifies N2O emissions at the kilometer-spatial scale in the wintertime in a region with both agricultural and urban sources, the San Joaquin Valley of California. To do this, we use the large number vertical profiles of N2O and other relevant trace gases measured by the P3 aircraft during the NASA DISCOVER-AQ campaign that took place throughout the San Joaquin Valley in January–February 2013. We exploit the observed variability in profile shape by time of day, day to day, and location (over urban versus agricultural sources), along with chemical and physical constraints on mixing and the timing of decoupling between the surface boundary layer and residual layers aloft.Author affiliations: 1University of Virginia, 2NASA Langley Research Center

Ecosystem function and the net benefit of services provided by three land-use types under variable management in northwestern Virginia Kelsey Huelsman, Howard Epstein

The concept of Ecosystem Services (ES) has become more interdisciplinary and influential in policy decision-making, but there are two major shortcomings in recent ES conversations: the resource inputs required by highly managed systems in order to provide material goods are not widely considered, and the distinction between ecosystem function and service is not always made. Supporting and regulating ES were examined for three land-use types with variable human management within the same mesoclimate: farmland, native prairie, and non-native early successional field. soil moisture readings and soil nitrogen (N) transformation incubations, biodiversity surveys, vegetation harvesting, and soil sampling in each land-use type were used to determine the following ES: habitat, productivity, soil fertility, nutrient cycling, and water retention. If the provision of a particular ES required human inputs or interference, its overall value was reduced by the environmental cost of management. Non-native early successional field is not valued for the provision of any particular ES, as native prairie and farmland are, but it provides supporting and regulating ES without the requirement of human intervention, making it valuable in different ways. Likewise, any ecosystem functions with negative ecological side effects were considered ecosystem disservices and reduced the overall value of ES provided by the system. For example, the function of net nitrogen mineralization, generally defined as a service, is a disservice under N-saturated conditions, as additional N could be lost via leaching or gaseous forms. This research is valuable in the context of the current trend of increasing farmland abandonment and land use conversions. By considering the cost of human management for the provision of certain ES, as well as potential disservices associated with function, the overall net benefits of these three land-use types can be compared to improve land-use decision-making.Author affiliations: Department of Environmental Sciences, University of Virginia

Tropospheric ozone (O3) is an air pollutant and key atmospheric oxidant. Global chemical transport models suggest 15–30% of tropospheric O3 is lost by deposition to the Earth’s surface annually. We require knowledge of O3 losses to predict O3 variability in the troposphere; however, there are few direct measurements of the atmosphere-surface loss rate, known as the deposition velocity, especially over heterogeneous plant canopies. Here, we describe a method for observationally-deriving the O3 deposition velocity using a flux-gradient approach combined with a light-weight low-power measurement payload onboard an unmanned aerial vehicle (UAV). Using indoor and outdoor test flight data, we demonstrate that combined uncertainties in O3 concentration and horizontal wind measurements are small enough to derive O3 deposition velocities of the order as those observed over a variety of vegetated landscapes. Here, we present UAV payload design, the derivation for deposition velocity, and preliminary flight data.Author affiliations: Department of Environmental Sciences, University of Virginia

Nitrogen Fertilizer Application to Virginia’s Eastern Shore: Refining Land Use and Fertilizer Estimates for the Seaward Side Rowan A. Johnson

Reactive nitrogen (Nr) inputs to the various watersheds on the seaward side of Virginia’s Eastern Shore from agricultural fertilizer, were estimated with a high-resolution GIS data layer in which active agricultural fields on the seaside of Virginia’s Eastern Shore were represented as individual polygons. Fields within the watersheds that feed the seaside lagoons were identified from the most recent high-quality air photos from the Virginia Base Mapping Program (VBMP) and manually digitized. Identification of fields under active cultivation was based on the presence of crops or tilling patterns and the absence of large areas of standing water in the photos. A total of 2038 individual fields were identified and outlined, and each field was assigned a crop rotation based on CropScape data [USDA, 2017] from 2013 through 2016. 84% of fields were identified as growing a corn, wheat, and soybeans rotation, but all rotations defined in CropScape were included. Based on this data layer, the total mass of Nr applied as fertilizer to these fields was estimated to be 2.03 x 106 kg N, annually. The average fertilizer application rate was estimated to be 123 kg N per hectare of cropland.

This land-use map was used in estimations of agricultural Nr inputs to the seaside lagoons for the entirety of the Virginia Eastern shore, but it can also be used on a watershed or sub-watershed scale to estimate Nr inputs to individual streams or bays. This tool will be useful in estimating agricultural Nr inputs upstream of water sampling locations, which can help researchers estimate how much Nr is removed by biological processes in various soils, aquifers, and creeks. This data layer yields less spatial error than CropScape alone, which has a lower resolution and often falsely categorizes abandoned fields or meadows as active cropland in our study area. This tool could also be used as a decision-making tool for management of Nr inputs to the seaside lagoons, and it could be expanded to include Bayside inputs as well.Author affiliations: Department of Chemistry, University of Virginia

Who is protected by the Clean Air Act? Dominique Ong, Carolyn Pugh, Laura Barry, and Sally Pusede

The purpose of the Clean Air Act (CAA) is to protect public health from air pollution. The U.S. Environmental Protection Agency (EPA) defines CAA compliance partly through the attainment of National Ambient Air Quality Standards (NAAQS) of six pollutants, including ozone (O3), nitrogen dioxide (NO2), and fine particulate matter (PM2.5). The EPA evaluates CAA NAAQS compliance by measuring the concentration of these six pollutants with a nation-wide monitoring network. Air pollution is often concentrated near sources and therefore the locations of the monitors are an important factor in determining subsequent regulations to improve air quality. It is well-documented that low-income and communities of color experience greater air pollution burdens. This study examines whether monitors are equitably sited within these communities. To do this, we combine O3, NO2, and PM2.5 monitor locations with 2010 U.S. census data. We compare mean minimum distances between monitors and census tracts in urban and rural areas and as a function of income, race, and age (seniors and children are more vulnerable to air pollution). Our early work on income, finds that low-income communities are located statistically significantly further from EPA monitoring stations, in both urban and rural areas, and that distance to monitors decreases with increasing average household income.Author affiliations: Department of Environmental Sciences, University of Virginia

The hydroxyl radical (OH) is the primary daytime atmospheric oxidant. The amount of OH determines the chemical lifetime of many compounds and drives the chemistry that produces air pollutants including ozone, nitric acid, and secondary aerosol. The OH concentration is a nonlinear function of nitrogen oxides (NOx). Over the past two decades, NOx emissions in the U.S. have decreased due to the effective regulatory control on NOx sources. These NOx controls have led to improvements in ozone air quality and nitric acid (acid rain), but also altered OH concentrations. While we have long-term measurements of ozone and nitrate, we do not have direct observational constraints on long-term trends in OH. Here, we propose to infer these trends in OH through variability in atmospheric concentrations of isoprene (C5H8), a reactive hydrocarbon emitted by plants, with a chemical lifetime against OH oxidation of less than an hour. Specifically, we use over 20 years of isoprene observations from sites across the U.S. to describe long-term trends in OH as a function of NOx and temperature.Author affiliations: 1Department of Environmental Sciences, University of Virginia, 2 Department of Chemistry, University of Virginia,3Department of Earth and Environment, Boston University

Salt marsh mallow (Kosteletzkya pentacarpos) is found in brackish marshes along the Atlantic and Gulf Coasts of the United States. K. pentacarpos is a perennial, non-clonal, herbaceous halophyte proposed as a crop plant in low-elevation agricultural fields experiencing salinization. These, and other, characteristics of this plant make it a promising species for facilitating high marsh development in agricultural fields impacted by sea level rise. In 2015, locally collected K. pentacarpos seeds were planted in an abandoned agricultural field where grain crops were grown as recently as 10 years ago. Plots (2 x 6 m) were established and divided in half with the midline marking the furthest expansion of Distichlis spicata communities in the field. One of four treatments were assigned to each half-plot without native marsh species and replicated in a three-block design. Treatments included tilled, tilled and drilled with K. pentacarpos, tilled and broadcasted with K. pentacarpos, and control plots that were left as they were found. K. pentacarpos seed germination, seedling survival, average plant height and seed production were measured in the first summer and fall. Observations of plant community composition focused on changes in abundance of D. spicata, Panicum virgatum, K. pentacarpos, and Phragmites australis. In year one, the community composition was dominated by native grass populations, including P. virgatum. After year two, D. spicata, K. pentacarpos, and P. australis cover increased in all treatment plots, while P. virgatum percent cover decreased. Disturbance of soil for planting allowed P. australis to invade the plots; however, D. spicata was compatible with salt marsh mallow cultivation, and colonization was increased relative to controls. These results suggest that growing K. pentacarpos in salinized agricultural fields may improve natural recruitment of high marsh plants species during marsh transgression from upland to salt marsh as sea level rises.Author affiliations: Department of Environmental Sciences, University of Virginia

Individuals can lower their environmental footprints by choosing to eat foods that use less carbon, water and reactive nitrogen to produce. The purpose of our research is to determine if a simple, yet informative labeling method can be used to systematically influence consumers to purchase more environmentally friendly food options.

This study took place at University of Virginia’s In the Nood Café, and tested the ability of two environmental impact labeling strategies to influence participants to purchase more environmentally friendly food. Participants were randomly assigned to one of three different conditions: (a) control, (b) menu with labels, or (c) priming plus menu with labels. Participants in the control condition answered filler survey questions before reviewing an In the Nood menu without environmental impact labels. Participants in the labeled menu condition answered filler survey questions before reviewing an In the Nood menu with environmental impact labels. Participants in the priming plus labeled menu condition answered a series of survey questions meant to spark thoughts about environmental protection before reviewing the menu with environmental impact labels. Data on the food items purchased by participants were collected through cross-referencing participant ID numbers from surveys to the receipts tracking food items purchased at the café.

Study results showed that participants in the priming plus labeled menu condition tended to order more sustainable foods than those in the control condition, but that the difference between those in the menu only condition and the control was not significant. Further analyses splitting the data by participant gender showed that labeling was effective in influencing females to buy more sustainable foods regardless of the presence or absence of a prime, but only the priming plus labeling condition was effective for males. These findings offer insight into labeling strategies that can be used to effectively promote more environmentally conscious decisions.Author affiliations: Department of Environmental Sciences, University of Virginia

It is well documented that biological processes at a broad range of biogeochemical scales and trophic levels are closely coupled with sea ice dynamics along the Western Antarctic Peninsula. This link is particularly pertinent since the region is one of the fastest warming on the planet and has seen large scale reductions in sea ice extent and ice duration. Most previous studies that examine the relationship between biology and ice rely on a few narrowly defined parameters (advance and retreat based on a 15% ice cover threshold, ice days and extent) that do not resolve the full gamut of ice characteristics. Ice type (e.g. fast, brash, frazil), thickness, snow cover, degree of deformation, concentration, floe size distribution, etc. are all parameters with biological relevance with impacts ranging from the surface metabolic balance and carbon export to direct impact on upper trophic levels like ice obligate krill and seals. In route to exploring ice-biology interactions we first assess ice itself. New satellite imagery (WorldView-2) allows us to improve resolution of sea ice along the Western Antarctic Peninsula by five orders of magnitude, exposing highly-fragmented ice floes and significant brash fractions that likely impact regional biological and physical processes and how we model them. Here we present a promising machine learning approach for the classification of sea ice in Antarctica.Author affiliations: Department of Environmental Sciences, University of Virginia

It has been proposed that the “flight to light” behavior of insects creates an ecological trap wherein insects are attracted to lit areas at night and are then unable to leave (Longcore & Rich 2004). Movement of consumers in or out of an area represents an important way that nutrients are exchanged across systems (Polis et al. 1997). If light pollution generally causes net attraction (attraction > repulsion) of insects, the net influx of insect biomass may cause light polluted areas to act as nutrient sinks. The primary objectives of this study are to (1) determine the extent to which light polluted areas increase attraction of invertebrates and (2) to utilize relationships from the literature to make predictions about the extent of nutrient redistribution via consumer movement in light polluted systems. We used three trapping methods targeting invertebrates with various movement patterns and incorporated a directional component for all traps to allow us to infer invertebrate movement in relation to light (e.g. attracted or repulsed). Preliminary results indicate variable effects of light pollution on different invertebrate orders. Pooled data from all arthropods caught in flight intercept traps demonstrate marginally significant attraction to our lit treatments compared with our control (unlit) treatment (P= 0.079-0.08). Lepidoptera were attracted to white LED lights (t12.98 = 2.24, P = 0.044), however Diptera exhibited repulsion from soft white LED lights (t15.00 = -1.764, P = 0.098). Future directions for this work will include identifying trapped invertebrates to family level to determine trophic position and carry out objective 2.Author affiliations: 1Department of Environmental Sciences, University of Virginia, 2Blandy Experimental Farm, University of Virginia, 3Howard University

Marine aerobic heterotrophic bacteria metabolize nearly half of the daily primary production in the ocean, playing a pivotal role in controlling export and carbon fluxes through food webs. We analyzed the 24-year time series (1989-2012) of bacterial and relevant ecosystem variables at the Bermuda Atlantic Time-series Study (BATS; 31º40’N, 64º10’W) site in the Sargasso Sea to explore the impacts of winter extratropical cyclones (storms) on the long-term trend and variability of bacterial processes. There was a long-term declining trend of bacterial production over the past 24-year period at BATS, without concurrent decreases in nutrient and carbon supply. During stormy winters phytoplankton biomass, primary productivity, and organic carbon pools were significantly elevated as storms induce deeper winter convective mixing and lead to increased nitrate fluxes into the upper ocean mixed layer. However, counter to expectation, bacterial production was significantly lower during stormy winters, suggesting that winter storms prevented bacteria from responding to increases in system productivity. Mechanistically, storm-induced inhibition of bacterial production was explained by entrainment of cold water into the upper mixed layer and temperature limitation on bacterial processes. Importantly, the frequency of storm-impacted months has increased over the past 24-years, driven by an increasing trend of winter mixed layer depth and a decrease of the North Atlantic Oscillation index, which appear to explain the observed decline of bacterial production at BATS. Based on these findings, we propose winter storms as a potential driver of the long-term decreasing trend of bacterial productivity, via temperature-dependent decoupling of bacteria from phytoplankton-supplied resources, ultimately impacting carbon fluxes and cycling in the subtropical North Atlantic region.Author affiliations: 1Columbia University/now at the University of Virginia, 2Columbia University

Opening Remarks, 2 pm

Clark Hall 108.

Special Session on Forest Growth and Resource Use in Response to Environmental Controls: 2:00 pm- 3:00 pm

Nitrogen deposition and precipitation frequency have been changing in recent decades, resulting in altered forest nitrogen and water availability. These changes are accompanied by varying responses in tree growth. Since topography is known to affect the spatial distribution of water and nutrient availability, spatial relationships within watersheds may shed light on forested ecosystems’ response to these long-term trends. While topographic controls on N and water availability have been researched extensively, less is known about how these effects alter tree growth.

This study aims to find the effect topography has on the growth patterns of Northern Red Oak and Chestnut Oak in three watersheds in Shenandoah National Park in Virginia, all of which have different base cation availability. Tree growth was measured by analyzing tree cores while soil nitrogen and water availability were measured through analysis of soil samples. Additionally, modelled data from the RHESSys model will be used to aid in finding within-watershed nitrogen and water availability. It is expected that tree growth will be enhanced under topography that promotes nutrient and water accumulation, such as areas in low elevation and converging terrain. However, saturated areas of N and water will have a negative effect on tree growth. Climate sensitivity of tree growth will also be higher under low N and water conditions. Additionally, water availability is expected to play a larger role in tree growth than nitrogen availability.Author affiliations: Department of Environmental Sciences, University of Virginia

Threshold behavior of stormflow response is an emergent pattern observed in several studies demonstrating subsurface storage controls on catchment rainfall-runoff dynamics. These studies demonstrate a distinct transition from negligible stormflow discharge response to rapid, linearly increasing stormflow identified by a single, uniquely-defined threshold as a basic catchment attribute that relates to geophysical properties. Utilizing precipitation, streamflow, and soil moisture data spanning 15 years from three catchments at the Coweeta Hydrologic Laboratory (CHL), we analyze how threshold behavior forms and varies at several timescales. We pose three hypotheses: (1) stormflow thresholds form at CHL as a function of antecedent soil moisture and gross precipitation, (2) thresholds vary seasonally and interannually, and (3) threshold variation through time implies greater long-term complexity of runoff controls beyond catchment geophysical properties, including forest canopy ecohydrologic feedbacks. We isolate threshold behavior of stormflow using piecewise regression analysis in short to long-term datasets with respect to antecedent soil moisture index and gross precipitation. We use this to investigate threshold variation over seasonal, interannual, and decadal timescales that encompass hydroclimatic extremes. Seasonal analysis reveals that thresholds are more variable between growing seasons than between dormant seasons. In growing seasons with greater water stress, stormflow thresholds are lower after controlling for soil moisture storage suggesting more complex, long-term rainfall-runoff relationships as a result of forest canopy response to water stress. We present a conceptual model of how vegetation-climate interactions influence long-term rainfall-runoff relationships creating interannual variability of stormflow thresholds and linear stormflow response.Author affiliations: 1Department of Environmental Sciences, University of Virginia, 2Environmental Sciences and Civil and Environmental Engineering, University of Virginia

Acid and nitrogen deposition have profoundly altered the biogeochemistry of eastern US forests in recent decades, but the long-term response of trees to anthropogenic deposition remains uncertain. We examined tree response to 25 years of whole-watershed ammonium sulfate addition at the Fernow Experimental Forest in West Virginia. Increment cores (n=15) were collected from Acer rubra (red maple), Liriodendron tulipifera (tulip poplar), Quercus rubra (northern red oak), and Prunus serotina (black cherry) in the treatment watershed, and in an adjacent control catchment. Significant differences in productivity were observed for red maple and tulip poplar in the treatment watershed compared to the control. Additionally, we examined climate-growth relationships to assess the influence of ammonium sulfate treatments on tree response to climate. Annual growth of all four species responded positively to metrics of water availability in the control watershed, whereas correlations between climate and tree growth were weak or nonexistent in the treatment watershed. Our results suggest that ammonium sulfate addition alters tree sensitivity to climate at Fernow, but future work should focus on the potentially divergent influences of N-fertilization and soil acidification on tree productivity and response to climate.Author affiliations: 1 Department of Environmental Sciences, University of Virginia, 2Rider University, 3University of New Hampshire, 4IUPUI

The emerald ash borer (EAB), Agrilus planipennis, is an invasive woodboring beetle native to Asia. EAB larvae feed on the inner bark of ash trees which disrupts the tree’s ability to uptake nitrate among other nutrients, ultimately leading to mortality. The EAB was first detected in southeastern Michigan in 2002 and, since then, has killed millions of ash trees in the northeastern United States. In 2013, the EAB was detected in Shenandoah National Park, Virginia. Recent increases in Shenandoah watershed stream nitrate concentrations are hypothesized to be a result of EAB-related ash tree mortality and consequential reduced nitrate uptake. This study investigates the proposed link between ash tree mortality and stream nitrate concentrations in 12 watersheds within Shenandoah National Park. Data analysis was conducted using high-resolution vegetation maps and long-term quarterly and annual stream nitrate data collected by the University of Virginia’s Shenandoah Watershed Study (SWAS) and the University of Maryland’s Appalachian Lab. Initial findings show strong relationships between elevated mean annual nitrate concentrations and watershed ash coverage. This research is significant because there are currently few physical signs of the emerald ash borer in Shenandoah ash trees. Because tree mortality does not occur until approximately five years after the initial infestation, a change in stream nitrate chemistry would be a first indication of EAB invasion.Author affiliations: 1Department of Environmental Sciences, University of Virginia, 2 University of Maryland

General Session III 3:00 pm- 4:00 pm

Clouds and their associated radiative effects are one of the largest sources of uncertainty in the present generation of global climate models. One region where model biases are especially large is over the Southern Ocean, where many models systematically underestimate the climatological shortwave cloud radiative effects (CRE) and/or misrepresent the relationship between shortwave CRE and atmospheric dynamics. Previous research has shown that two “cloud controlling factors”, estimated inversion strength (EIS) and mid-tropospheric vertical velocity, are helpful in explaining the relationship between CRE and atmospheric dynamics on monthly timescales. For example, when the Southern Hemisphere midlatitude jet shifts poleward on monthly timescales, the high clouds and their associated longwave CRE shift poleward with the jet, consistent with a poleward shift of the storm track and the attendant vertical velocity anomalies. However, the observed changes in shortwave CRE with a poleward jet shift are small due to a trade-off between the competing effects of opposing EIS and vertical velocity anomalies.
This study extends these previous findings to examine the relationship between Southern Ocean cloud controlling factors and CRE on daily timescales. On a daily timescale, the relationship of EIS and vertical velocity with CRE is more complex, due in part to the presence of transient weather systems. Composites of EIS, vertical velocity, longwave CRE, and shortwave CRE around extratropical cyclones and anticyclones are constructed to examine how the CRE anomalies vary in different sectors of midlatitude weather systems and the role that EIS and vertical velocity play in determining those anomalies. The relationships between the cloud controlling factors and CRE on daily timescales provide key insight into the underlying physical processes responsible for the relationships between midlatitude cloud controlling factors and CRE previously documented on monthly timescales.Author affiliations: Department of Environmental Sciences, University of Virginia

Drought severity and frequency are predicted to increase in the future due to climate change. Drought conditions are expected to affect ozone air pollution, potentially altering both ozone production and the atmospheric ozone lifetime. However, the magnitude of drought effects on ozone pollution are uncertain because it has proven difficult to disentangle impacts to ozone production from loss. We present an analysis of long-term field data that separates impacts to production and loss terms. We demonstrate that during California’s recent severe drought, emissions of biogenic reactive organic carbon decreased to an extent that there was a change in the dominant atmospheric chemical oxidations mechanisms producing ozone. We also quantitatively bound diminished ozone loss to deposition and chemistry. We observe that this change in atmospheric composition and chemistry has persisted for at least two years since the drought’s end.Author affiliations: 1Department of Environmental Sciences, University of Virginia, 2Saint Mary’s College-University of Notre Dame, Chemistry, 3Department of Earth and Environment, Boston University

Plant species differ in both the quantity and quality of pollen they offer pollinators, potentially influencing foraging preferences among bumblebees who rely on pollen rewards for protein. Bumblebees exhibit diurnal patterns in plant visitation rates in a controlled setting; however, it is not understood if pollen collection varies diurnally in wild bumblebees and how quantity of pollen resources influences daily foraging preferences. The goal of the research is to test the following questions: 1) what is the availability of primary pollen resources in the field and how do they vary diurnally and 2) how does the availability of primary pollen resources influence daily pollen collection in wild bumblebees? To estimate resource availability, I counted pollen from field-collected inflorescences of Carduus acanthoides, Securigera varia, Solanum carolinense, and Verbascum thapsus in both the morning and afternoon in early and late July in a successional field at Blandy Experimental Farm. These four species make up over 90% of the pollen collected by bumblebees at Blandy. To quantify pollen collection, I collected the pollen loads of foraging bumblebees in both the morning and afternoon from the field in late June and mid-July, identifying pollen species with microscopy. I found significant resource drawdowns in all plant species except S. varia in early July, but only in V. thapsus in late July. I also found significant differences in the pollen load compositions between the morning and the afternoon in both late June and mid-July. Pollen resource availability appeared to be a significant driver of bumblebee pollen collection throughout the day in the late June sample with B. griseocollis and B. impatiens pollen collection shifting from less abundant pollen resources towards more abundant resources (S. varia) in afternoon. This study shows that bumblebees exhibit diurnal fluctuations in pollen collection, providing a more complete understanding of their diet.Author affiliations: 1University of Virginia, 2Blandy Experimental Farm, University of Virginia

Eutrophication and species introductions have resulted in increased macroalgal biomass in coastal ecosystems around the globe. Macroalgal mats may compete with microphytobenthos (MPB) for light and nutrients and due to their position in the canopy, have a negative impact on MPB biomass. We tested this effect by conducting a meta-analysis of prior experiments as well a comparative survey and a macroalgal-removal manipulation in the coastal lagoons of the Virginia Coastal Reserve (VCR) on the eastern shore of Virginia (U.S.A.). While prior individual studies documented impacts of macroalgae, when effect sizes were averaged across studies, there was no significant effect of macroalgal biomass on MPB. In the VCR a non-native red macroalga, Gracilaria vermiculophylla, dominates intertidal mats and attains high biomasses at some sites. Nevertheless, macroalgal biomass was unrelated to MPB based on a survey of mudflats. Further, when macroalgae were removed from a mudflat using a before and after impact design, there was no change in MPB relative to a reference. Based on the meta-analysis, survey, and manipulation we conducted, macroalgal mats do not generally have a negative effect on MPB. This finding is important given the significance of MPB in supporting food webs and other estuarine ecosystem functions, and the increasing frequency and intensity of macroalgal blooms.Author affiliations: Department of Systems and Information Engineering, University of Virginia